While most of you post is accurate, I would point out one other factor that drove the creation of the tri party repo market. While the risk of not being able to turn around returned securities was a contributing factor, my memory of Salomon Brothers' creation of the tri party product was that it was driven by one of our repo counterparts that complained about taking down numerous lines of collateral over the phone each day and then having to write out multiple tickets to input the trades. I believe the customer was SecPac Bank. They suggested to us that a better alternative would be for a third party to preform the trade input on their behalf and ensure that the collateral remain properly priced. The repo defaults of the mid 1980's illustrated the value of tri party and from that point it became the market standard.